WO2017134290A1

WO2017134290A1 - Skid for subsea modules

Info

Publication number: WO2017134290A1
Application number: PCT/EP2017/052498
Authority: WO
Inventors: Alexander Piltingsrud GREVSTAD
Original assignee: Fmc Kongsberg Subsea As
Priority date: 2016-02-05
Filing date: 2017-02-06
Publication date: 2017-08-10
Also published as: NO341953B1; NO20160205A1

Abstract

The present invention provides a skid (1) for handling subsea modules (2), comprising a bottom section (3) and at least one vertical guidepost (4), wherein the at least one vertical guidepost (4) is for interaction with an intervention tool (5) having a connecting interface (6) for a subsea module (2); and the bottom section (3) comprises a transfer assembly comprising at least two docking sites (8), wherein each of the at least two docking sites (8) is able to accommodate a subsea module (2) and is movable in the horizontal plane such that each of the at least two docking sites (8) may be sequentially arranged at the same position in the skid.

Description

SKID FOR SUBSEA MODULES

Field of the invention

The present invention relates to the field of skids for intervention tools, and more particularly to skids for subsea modules and methods for replacing such subsea modules.

Background

In subsea systems, a number of different types of subsea modules, for instance subsea control modules (SCMs), must be replaced after a certain time period.

In present operations or methods for replacing subsea modules, the subsea modules are stored in a storage area on deck of the vessel used in the operation. During the operation, subsequent to retrieval of a used subsea module to be replaced from a subsea structure, a new subsea module is first transferred to a skid arranged on the deck. After retrieving the used subsea module by a multipurpose intervention tool (MIT), the MIT is raised up into the moonpool handling tower of the vessel, an empty skid is skidded from the storage area and into the moonpool handling tower and the used subsea module is transferred to the skid. The skid featuring the used subsea module is then skidded out of the handling tower. The skid featuring the new subsea module is then skidded from the storage area and into the handling tower.

The MIT is lowered to the skid and the new subsea module is installed/loaded into a connecting interface on the MIT. The MIT is then lifted away from the skid, the skid is removed from the handling tower and the MIT is lowered to the subsea structure and the new subsea module is installed.

Due to the required deck handling of the subsea modules, the present methods for replacing subsea modules are both difficult and unsafe to perform in offshore conditions with wave heights above 3-4 meters. In addition, the present methods are time consuming, requiring 1-2 hours of operation time for deck handling of the subsea modules, i.e. transferring the new subsea module to a skid before

transferring the skid to a moonpool, and unloading the used subsea module from the skid after retrieving it from the subsea structure.

WO 2012/110289 A2 discloses a skid comprising a test stump for receiving various subsea well equipment. The test stump is adapted to move in and out of a test position on a support body of the skid.

Thus, the goal of the present invention is to provide a method which avoids at least some of the disadvantages of the prior art methods, as well as a skid for subsea modules suitable for such a method. Summary of the invention

The present invention is defined in the appended claims and in the following: In a first aspect, the present invention provides a skid for handling subsea modules, comprising a bottom section and at least one vertical guidepost, wherein

the at least one vertical guidepost is for interaction with an intervention tool having a connecting interface for a subsea module; and

the bottom section comprises a transfer assembly comprising at least two docking sites, each of the at least two docking sites is able to

accommodate a subsea module and is movable in a horizontal plane such that each of the at least two docking sites may be sequentially arranged at the same position in the skid.

The same position in the skid, at which that at least two docking sites may be sequentially arranged, is the position at which the connecting interface of the intervention tool may retrieve or transfer a subsea module when the intervention tool is landed on the skid. In other words, the at least two docking sites may be sequentially arranged at the same position in the skid such that an intervention tool may transfer a subsea module to or from said same position.

The connecting interface of the intervention tool is for accommodating, retrieving and/or delivering a subsea module to/from a subsea structure or a docking site on the skid.

In one embodiment of the skid, the transfer assembly comprises a transfer element comprising the at least two docking sites, and the transfer element is movable in a horizontal plane, such that the at least two docking sites will have a linear and/or curved movement allowing them to be sequentially arranged at the same position in the skid.

In one embodiment of the skid, the transfer element is a carousel element able to rotate in the horizontal plane.

In one embodiment of the skid, an upper part of the at least one guide post is able to interact with the intervention tool while at least one of the at least two docking sites is accommodating a subsea module and is moved in the horizontal plane.

In one embodiment of the skid, the at least one vertical guidepost is arranged such that the connecting interface for a subsea module of the intervention tool may be lowered to one of the at least two docking sites for receiving or delivering a subsea module.

In one embodiment of the skid, the movement of the at least two docking sites may be remotely operated, preferably by use of a hydraulic or electric motor or piston. In one embodiment of the skid, the transfer assembly comprises at least one storage docking site able to accommodate a subsea module, the at least one storage docking site is connectable to the transfer element via a skid track, such that a subsea module arranged on the at least one storage docking site may be transferred to one of the docking sites of the transfer element. In embodiments of the skid featuring at least one storage docking site, each of the subsea modules may be arranged on a separate base unit being movable on the skid track, such that the subsea modules may be skidded to a docking site from the storage docking site, and vice versa, upon their respective base units. The base unit may comprise connecting means for securing the subsea module on the base unit. Such connecting means may for instance be a threaded pin.

In one embodiment, the skid comprises a remotely operated winch system or piston for transferring a subsea module from the at least one storage docking site to one of the docking sites of the transfer element, or vice versa.

In a second aspect, the present invention provides a transfer assembly for arrangement on a bottom section of a skid comprising at least one vertical guidepost for interaction with an intervention tool having a connecting interface for a subsea module, wherein the transfer assembly comprises at least two docking sites, each docking site able to accommodate a subsea module, and is movable in a horizontal plane, such that any one of the at least two docking sites may be sequentially arranged at the same position relative to the bottom section of the skid. The same position relative to the bottom section of the skid is a position identical to the same position in the skid defined above.

In one embodiment, the transfer assembly comprises a transfer element comprising the at least two docking sites, and the transfer element is movable in the horizontal plane, such that the at least two docking sites will have a linear and/or curved movement allowing them to be sequentially arranged at the same position in the skid.

The transfer assembly according to the second aspect may comprise any of the features defined for the transfer assembly in the skid according to the first aspect.

In a third aspect, the present invention provides a method for replacing a first subsea module on a subsea structure with a second subsea module, comprising the steps of: lowering an intervention tool, comprising a connecting interface for a subsea module, to the subsea structure; connecting the first subsea module to the connecting interface;

retrieving the first subsea module from the subsea structure by lifting the intervention tool;

arranging a skid according to the first aspect above, wherein a first docking site, of the at least two docking sites, is empty and a second docking site, of the at least two docking sites, accommodates the second subsea module, in a handling tower of a moonpool;

landing the intervention tool on the skid;

transferring the first subsea module from the connecting interface to the first docking site on the skid;

lifting the intervention tool to allow movement of the first and the second docking sites;

moving the first and the second docking sites, such that the second docking site and the second subsea module is at a position below the connecting interface;

lowering the intervention tool to bring the connecting interface into connection with the second subsea module;

lifting the intervention tool away from the skid;

lowering the intervention tool comprising the second subsea module to the subsea structure for installation; and

installing the second subsea module on the subsea structure.

The method may further comprise a step of disconnecting the second subsea module from connecting means on the second docking site prior to the step of landing the intervention tool on the skid.

In one embodiment, the method comprises a step of loading at least the second subsea module onto the second docking site of the skid preceding the step of landing the intervention tool on the skid.

In one embodiment, the method comprises an initial step of loading multiple subsea modules onto multiple docking sites of the skid.

In one embodiment of the method, the initial step is prior to mobilization of a vessel from which the method is performed.

In a fourth aspect, the present invention provides for the use of a skid according to the first aspect, or a transfer assembly according to the second aspect, in the replacement or installation of a subsea module on a subsea structure.

In one embodiment of the skid, transfer assembly or method, the transfer element comprises three, four or five docking sites. The docking sites may comprise connecting means for releasably securing the subsea modules. Such connecting means may for instance be a threaded pin (as used in securing subsea control modules onto a skid). In one embodiment of the skid, transfer assembly or method, the subsea modules are subsea control modules.

The term "intervention tool" is intended to encompass any type of suitable intervention tool, such as a multipurpose intervention tool (MIT).

Short description of the drawings

The present invention is described in detail by reference to the following drawings: Fig. 1 is a perspective view of a first embodiment of a skid according to the invention.

Fig. 2 is a perspective view of the embodiment in fig. 1 , the view showing the opposite side of the skid.

Fig. 3 is a schematic top side view of a second embodiment of a skid according to the invention.

Figs. 4-9 are schematic views illustrating a method according to the invention.

Figs. 10- 11 are schematic top side views of a third embodiment of a skid according to the invention.

Detailed description of the invention

The present invention is described in detail by reference to a skid and a method for replacing subsea control modules (SCMs) on a subsea structure. The subsea structure may be any type of structure, such as X-trees, manifolds etc. The invention is equally applicable to any type of subsea module.

Opposite sides of a skid 1 according to the invention is shown in figs. 1 and 2. The skid comprises a bottom section 3, a supporting framework 9, an SCM transfer assembly (i.e. a transfer assembly) and two vertical guideposts 4. The SCM transfer assembly is arranged on, or as a part of, the bottom section 3 and features a carousel/turntable (i.e. a transfer element) having three docking sites. An SCM may be arranged upon each docking site, and the carousel may be turned in the horizontal plane such that the positioning of each docking site, and thus each SCM, may be changed. The SCM' s are commonly secured to their respective docking sites by a threaded pin arranged on the docking site. The two vertical guideposts are arranged to interact with cooperating guide funnels 10 of a multipurpose

intervention tool 5 (MIT) (i.e. an intervention tool), and ensures that said tool is correctly positioned when landed on the skid 1. The MIT comprises a connecting interface 6 adapted for releasably connecting to an SCM 2. By turning the carousel any of the docking sites, and consequently any SCM 2 arranged on a docking site, may be positioned below the connecting interface of the MIT. The two vertical guide posts (or alternatively the cooperating guide funnels) are preferably long enough to provide guidance to the MIT while also allowing unhindered operation of the carousel (i.e. allowing an SCM to be position below the connecting interface 6 while still providing guidance to the MIT). The movement/turning of the carousel is preferably remotely operated by use of a hydraulic/electric motor or piston.

In figs. 1 and 2, the skid is loaded with two SCMs 2a,2b, each arranged on a separate docking site 8' , while one of the docking sites 8 is unoccupied. In use, an MIT featuring a used SCM to be replaced from a sub sea structure may be landed on the skid 1, the used SCM disconnected/unloaded from the MIT and positioned on the unoccupied docking site. After unloading of the used SCM, the MIT is raised to allow for rotation of the carousel such that a new SCM is positioned below the connecting interface 6 of the MIT. The MIT is then lowered, the new SCM connected to the connecting interface, and the MIT featuring the new SCM may then be raised and subsequently lowered to a subsea structure, wherein the new SCM is installed. These steps may be repeated a number of times depending on the number of docking sites and SCMs available on the skid. Thus, by use of a skid according to the invention, a number of advantages are achieved. These advantages include avoiding deck handling of the SCMs while at sea, making it possible to perform operations in offshore conditions with wave heights above 4 meters. The performed offshore operations are further less time consuming than the present methods since multiple SCMs may be arranged on the skid prior to mobilization of the vessel from which the operation is performed.

Another embodiment of a skid according to the invention is shown as a schematic horizontal cross-section in fig. 3. In this embodiment, the carousel 7 (i.e. transfer element) comprises four docking sites 8. In addition, three storage docking sites 11 are arranged on, or in, the bottom section 3 adjacent the carousel 7. Each of the storage docking sites are connected to the circumference of the carousel by a first set of skid tracks 12a, and each of the docking sites are connected to the

circumference of the carousel by a second set of skid tracks 12b. The first and the second set of skid tracks are aligned such that they provide a single skid track 12 when a docking site is positioned adjacent one of the storage docking sites. The single skid track allows a subsea control module to be skidded from a storage docking site to a docking site, and vice versa, provided one of the storage docking site or the docking site is free. The feature of having three storage docking sites (i.e. at least one storage docking site) on the bottom section allows for the loading of up to six SCMs onto the skid (in case of a pure installation operation, i.e. an operation wherein no used SCMs are replaced, the skid may be loaded with seven SCMs). The skidding of a new SCM from a storage docking site to a docking site (or vice versa) may be obtained by use of any suitable arrangement, such as a manually or remotely operated winch system 13 or suitably arranged hydraulic cylinders.

A skid according to the invention may advantageously be used in a method for replacing a used SCM arranged on a subsea structure. The various steps performed during such a method are described by reference to the figs. 4-9. Figs. 4-9 show the various steps illustrated as schematic horizontal cross-sections of a skid according to the invention 1, a multipurpose intervention tool 5 (MIT) and a handling tower 14 arranged above a moonpool. Preceding the method illustrated by figs. 4-9, the skid has been loaded with the required number of SCMs to be replaced. The SCM loading operation may advantageously be performed before the vessel from which the method is performed is mobilized.

In a first step, the multipurpose intervention tool (MIT), comprising a connecting interface 6 for a subsea control module 2a,2b is lowered to the subsea structure, wherein a used subsea control module 2a (i.e. a first subsea module) is connected to the connecting interface 6. The used subsea control module 2a is retrieved from the subsea structure by lifting/raising the MIT. Before the MIT may be lowered to the subsea structure, the skid is skidded into the handling tower 14, as indicated by the bold arrows, the MIT lifted off the skid, and the skid skidded out of the handling tower, see fig. 4. Similarly, the skid is skidded into the handling tower after the used subsea control module is retrieved and the MIT have been lifted up into the tower, see fig. 5.

When the used subsea control module 2a has been retrieved and the skid arranged below the MIT, the MIT is landed onto the skid, see fig 6. The used subsea control module 2a is positioned at an empty docking site 8 and disconnected from the connecting interface 6 of the MIT. The MIT is then raised to allow rotation of the carousel 7 (indicated by bold arrows fig. 7), such that a new subsea control module 2b (i.e. a second subsea module) is positioned at a point below the connecting interface 6 (i.e. arranged at the position previously occupied by the used subsea control module), see fig. 8. When the new SCM has been arranged at the position below the connecting interface 6, the MIT is lowered and the connecting interface is brought into contact with and connected to the new SCM 2b. The MIT is then raised away from the skid, and the skid is skidded out of the handling tower, see fig. 9. The MIT is then lowered to the subsea structure for installation of the new SCM. By repeating the above steps, the method may be used for replacing or installing multiple SCMs. Yet another embodiment of a skid according to the invention is shown as a schematic horizontal cross-section in figs. 10 and 11. In this embodiment, the transfer element is not a carousel as in the above described skid, but a platform 15 (i.e. transfer element) featuring two docking sites 8. The platform may be moved in a linear direction such that the two docking sites may be sequentially arranged at the same position, i.e. the position below the connecting interface of an MIT as shown above. With reference to the method described above, the skid in fig. 10 would correspond to the situation shown in fig. 7 and fig. 1 1 would correspond to the situation in fig. 8. The platform is slidably connected to the bottom section of the skid by for instance being arranged on rails (not shown) to facilitate the linear movement.

The disclosed skid, transfer assembly and method, provides a number of

advantages, such as:

- HSE hazards are removed;

Operations are not weather dependable;

No manual handling or lifting of SCM during deck handling;

1-2 hours of operation time saved during deck handling, which translates into a reduction in well shutdown time of 1-2 hours;

- Vessel mobilization time is reduced;

Less lifts and sea fastening during vessel mobilization;

Reduced possibility of damaging the SCM during deck handling; and

Less skidding of pallets/skids during operation.

Claims

A skid (1) for handling subsea modules (2), comprising a bottom section (3) and at least one vertical guidepost (4), wherein

the at least one vertical guidepost (4) is for interaction with an intervention tool (5) having a connecting interface (6) for a subsea module (2); and

the bottom section (3) comprises a transfer assembly comprising at least two docking sites (8), wherein each of the at least two docking sites (8) is able to accommodate a subsea module (2) and is movable in the horizontal plane such that each of the at least two docking sites (8) may be sequentially arranged at the same position in the skid.

The skid according to claim 1, wherein the transfer assembly comprises a transfer element (7) comprising the at least two docking sites, and the transfer element is movable in the horizontal plane, such that the at least two docking sites (8) will have a linear and/or curved movement allowing them to be sequentially arranged at the same position in the skid.

The skid according to claim 2, wherein the transfer element is a carousel element able to rotate in the horizontal plane.

The skid according to any of the preceding claims, wherein an upper part of the at least one guidepost (4) is able to interact with the intervention tool (5) while at least one of the at least two docking sites is accommodating the subsea module (2) and is moved in the horizontal plane.

The skid according to any of the preceding claims, wherein the at least one vertical guidepost (4) is arranged such that the connecting interface (6) for a subsea module (2) of the intervention tool (5) may be lowered to one of the at least two docking sites (8) for receiving or delivering a subsea module.

The skid according to any of the preceding claims, wherein the movement of the at least two docking sites may be remotely operated.

The skid according to any of the claims 2-6, wherein the transfer assembly comprises at least one storage docking site (11) able to accommodate the subsea module (2), the at least one storage docking site is connectable to the transfer element (7) via a skid track (12), such that the subsea module arranged on the at least one storage docking site (1 1) may be transferred to one of the docking sites (8) of the transfer element (7).

8. The skid according to claim 7, comprising a remotely operated winch system (13) or piston for transferring a subsea module from the at least one storage docking site (11) to one of the docking sites (8) of the transfer element, or vice versa.

9. A transfer assembly for arrangement on a bottom section (3) of a skid

comprising at least one vertical guidepost (4) for interaction with an intervention tool (5) having a connecting interface (6) for a subsea module (2), characterized in that the transfer assembly comprises at least two docking sites (8), each docking site (8) is able to accommodate the subsea module (2), and is movable in the horizontal plane, such that any one of the docking sites (8) may be sequentially arranged at the same position relative to the bottom section (3) of the skid.

10. A transfer assembly according to claim 9, comprising a transfer element (7) comprising the at least two docking sites, and the transfer element is movable in the horizontal plane, such that the at least two docking sites (8) will have a linear and/or curved movement allowing them to be sequentially arranged at the same position in the skid

11. A method for replacing a first subsea module (2a) on a subsea structure with a second subsea module (2b), comprising the steps of: lowering an intervention tool (5), comprising a connecting interface (6) for a subsea module (2a,2b), to the subsea structure;

connecting the first subsea module (2a) to the connecting interface (6); retrieving the first subsea module (2a) from the subsea structure by lifting the intervention tool;

arranging a skid (1) according to any of the claims 1-8, wherein a first docking site (8), of the at least two docking sites, is empty and a second docking site, of the at least two docking sites, accommodates the second subsea module (2b), in a handling tower (14) of a moonpool;

landing the intervention tool on the skid (1);

transferring the first subsea module from the connecting interface (6) to the first docking site on the skid;

moving the first and the second docking sites, such that the second docking site and the second subsea module (2b) is at a position below the connecting interface (6);

lowering the intervention tool to bring the connecting interface (6) into connection with the second subsea module; lifting the intervention tool away from the skid;

removing the skid from the handling tower;

lowering the intervention tool comprising the second subsea module (2b) to the subsea structure for installation; and

- installing the second subsea module on the subsea structure.

12. The method according to claim 11, comprising a step of loading at least the second subsea module onto the second docking site of the skid preceding the step of landing the intervention tool on the skid.

13. The method according to claim 11 orl2, comprising an initial step of loading multiple subsea modules onto multiple docking sites of the skid.

14. Use of a skid according to any of the claims 1-8, or a transfer assembly

according to any of the claims 9- 10, in the replacement or installation of a subsea module on a subsea structure.